Feather-Trace: add support for locking-related syscall overheads

Support recording timestamps that allow tracing the entry and exit
costs of locking-related system calls.

2 files changed, 22 insertions, 0 deletions

diff --git a/include/litmus/litmus.h b/include/litmus/litmus.h
index 807b7888695a..f7893ef18162 100644
--- a/include/litmus/litmus.h
+++ b/include/litmus/litmus.h
@@ -259,4 +259,20 @@ static inline quanta_t time2quanta(lt_t time, enum round round)
 /* By how much is cpu staggered behind CPU 0? */
 u64 cpu_stagger_offset(int cpu);
 
+static inline struct control_page* get_control_page(struct task_struct *t)
+{
+        return tsk_rt(t)->ctrl_page;
+}
+
+static inline int has_control_page(struct task_struct* t)
+{
+        return tsk_rt(t)->ctrl_page != NULL;
+}
+
+
+#define TS_SYSCALL_IN_START                                             \
+        if (has_control_page(current)) {                                \
+                __TS_SYSCALL_IN_START(&get_control_page(current)->ts_syscall_start); \
+        }
+
 #endif
diff --git a/include/litmus/rt_param.h b/include/litmus/rt_param.h
index fac939dbd33a..6456ed04fddb 100644
--- a/include/litmus/rt_param.h
+++ b/include/litmus/rt_param.h
@@ -89,8 +89,14 @@ union np_flag {
  * determining preemption/migration overheads).
  */
 struct control_page {
+        /* This flag is used by userspace to communicate non-preempive
+         * sections. */
         volatile union np_flag sched;
 
+        /* Locking overhead tracing: userspace records here the time stamp
+         * prior to starting the system call. */
+        uint64_t ts_syscall_start; /* Feather-Trace cycles */
+
         /* to be extended */
 };